The Protein Purification Core will provide support to all projects by providing facilities and skills for isolating and purifying native and recombinant proteins. Raw materials for such preparations will be provided by the individual projects, along with suggested methods for the isolations. Protein isolations will be carried out the senior Core technician (50% effort), with supervision by Core leader (5% effort). A Pharmacia AKTA explorer Protein Purification System is requested to assume efficient use of time and materials. Purified proteins will by characterized by spectrophotometry, SDS-gel electrophoresis and, in special cases, by EPR spectroscopy. The Core will serve all projects, with heaviest use by Project 1 (Mechanisms of Cellular Iron Uptake From Transferrin, Project 2 (Functional Domains of the Transferrin Receptor), and Project 5 (Structure, Function and Dynamics in Transferrin), and less demanding use by Project 3 (Uptake of Transferrin and Non- transferrin Bound Fe by SFT) and Project 4 (Role of Copper in Iron Metabolism).